The invention relates generally to valve features for avoiding contamination of operating valve parts from internally produced particles, and more specifically to a solenoid valve design in which a vertically movable stem carrying a valve closure member and a guide structure in which the stem moves are specifically configured to prevent particulate matter from entering the bearing clearance between the stem and guide structure.
Particulate contamination of solenoid operated valves is a well recognized problem. Particulate matter in fluid medium surrounding the valve seat and closure member may be deposited on the seat and/or closure member, where it tends to impair closure and/or sealing of the valve. In addition, particles may become lodged in the clearance space between the valve stem and guide structure, where they may interfere with or preclude free movement of the stem and closure of the valve.
A filter and/or sediment trap in the form of a drip leg or a labyrinth or baffle structure is frequently provided at the supply side of a gas valve to catch particles entrained in the supply gas. However, such an arrangement does not protect against particles produced within the valve. Specifically, wear particles from the movable parts of the solenoid operator may be unavoidable even though the parts are carefully machined or formed. The wear particles occur as one part slides over or strikes against another part, and, understandably, are more prevalent in frequently actuated solenoid valves.
The previously described problem is particularly significant in valves of a design having a solenoid with a vertically movable armature above a valve closure member carried on a vertically movable stem. In such a design, gravity, sometimes assisted by pressure changes within the operator which occur upon actuation thereof, tends to move the particles toward the closure member and valve seat.
A variety of approaches have been conceived for eliminating or minimizing the migration of wear particles or other particulate matter from a solenoid operator into the vicinity of the valve seat/closure member. For example, German Patent Document DE 31 35 261 A1 discloses a solenoid valve in which the region of the valve through which the controlled fluid is intended to flow is sealed from the solenoid operator components by means of a metal bellows.
Another approach is shown in U.S. Pat. No. 4,947,890 which discloses a solenoid valve having an armature horizontally guided in a sleeve with radial fluid flow ports therein. Radial flow at the end of the armature tends to divert any particulate matter away from the annular clearance space between the armature and the sleeve. In certain of the disclosed embodiments, the sleeve is formed with a step increase in internal diameter or the armature is formed with step decrease in external diameter to accommodate foreign matter which may be deposited. In yet another disclosed embodiment, baffles are incorporated into the fluid flow passageway, the baffles tending to collect particles which may be present in the fluid whose flow is being controlled.
Although the above described and other valve designs have been devised for avoiding problems caused by foreign matter entering the flow passageway of a valve from the valve actuator, there is a continuing need for simpler design features which address the problems in an effective manner.